Sensitizing of bleaching-out layers



Patented Apr. 24, 1934 UNITED STATES SENSITIZING OF BLEAOHING-OUT LAYERS I Bruno Wendt and Alfred Friihlich, Deccan in Anhalt, Germany, assignors to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York No lirawing. Application August 1, 1932, Serial No. 627,220. In Germany August 4, 1931 Claims.

Our present invention relates to sensitizing colloid layers containing bleaching-out dyes.

One of its objects is to incorporate the sensitizer in the finished bleaching-out dye layer.

5 Other objects are the different methods of incorporating the sensitizer in the finished bleachingout dye layer. Further objects will be seen from the detailed specification following hereafter.

We have found that it is most convenient to lo incorporate an organic sensitizer, for instance, thiosinamine in the finished bleaching-out dye layer before the same is used. By incorporating the sensitizer only at this stage, the stability of these layers is considerably increased. The incorporation of the sensitizer may occur in various manners. For instance, a solution of the sensitizer may be applied to the colloid layer consisting, for instance, of gelatin or a cellulose derivative and containing the bleaching-out dyes, by

means of rollers wetted with the solution in any suitable manner, or the solution may be applied by spraying the bleaching-out layer either with the solution itself or with the solution in admixture with a colloid.

In order to avoid a wet treatment, the sensitizer may be applied to the layer in the form of vapour in which case, the vapour of sensitizer may be produced in a closed vessel in the presence or absence of other volatile substances, if required under a reduced pressure and while heating.

It is also possible to allow the sensitizer to diffuse from a suitable carrier into a bleachingout layer. The diffusion occurs without aid or is helped by gentle heating (ironing) or by moistening. As a carrier for the sensitizer there may be used paper or a colloid layer (a sheet of gelatin, regenerated cellulose, cellulose esters, cellulose ethers, etc). The carrier is impregnated with a solution of the sensitizer, or the sensitizer is incorporated in the carrier already during its manufacture, by adding it, for instance, to the gelatin solution or the solution of a cellulose derivative before being poured on the support to form a sheet. Such a colloid layer containing the sensitizer may if desired be applied to any suitable base. Whcn the colloid layer provided with the sensitizer is brought into contact with the bleaching-out layer the sensitizer diffuses into the bleaching-out layer under the conditions above mentioned. After the sensitizer has diffused into the bleaching-out layer, thepressed-on carrier for the sensitizer can be detached, or if it consists of a transparent material, it may remain on the bleaching-out layer during the printing process.

The process according to this invention may also be used for the manufacture of sensitized bleaching-out layers on a commercial scale by first preparing non-sensitized layers which are stored in this state. correspondingly with demand of sale, the stored non-sensitized layers are provided in known manner by any of the usual coating machines or by means of a spraying device with the colloid coating. (gelatin or a cellue lose derivative), which contains the quantity required of sensitizer. 85

The following examples illustrate the invention.

Example 1.Diethylallylthiourea and twice its weight of alcohol are evaporated in a closed otherwise evacuated chamber, preferably by gently heating, in thepresence of a bleaching-out layer, for instance, a colloid layer consisting of 30 per cent of collodion and '10 per cent of ethylbenzylcellulose containing bleaching-out dyes and applied to a paper support. The bleaching-out layers are left therein (for about 10 minutes), un til the degree of sensitizing desired is attained.

Example 2.-A solution of 0.8 gram of nitrocellulose and 1.0 gram of pyperidylallylthlourea in 75 cc. of a mixture of 1 part of alcohol and 3 parts of ether is poured on 800 square centimeters of Cellophane (registered trade-mark) or pergamyn. The sheet is pressed on a non-sensitized bleaching-out layer as indicated in Example 1 be-. tween heated rollers or by means of a-fiatiron. After a short time the sensitizer is uniformly distributed in the bleaching-out layer and the sensitizing sheet, whereupon the latter is detached from the bleaching-out layer;

Example 3.A solution of 5 grams of allylthiourea, 100 cc. of water and 8 grams of gelatin is poured so as to form a layer 10 a thick onto a bleaching-outlayer comprising gelatin as binding agent.

Example 4.A solution consisting of 2 grams of dimethylallylthiourea, 1.5 gram of ethylbenzylcellulose, 0.5 gram of nitrocellulose, 20 cc. of ether, 40 cc. of alcohol and 40 cc. of benzene is sprayed onto a bleaching-out layer according to Example 1 by means of a spraying gun. After drying the bleaching-out layer is ready for use.

What we claim is:

1. In sensitizing bleaching-out layers the step which comprises incorporating the sensitizer in the finished bleaching-out layer by applying to the bleaching-out layer a colloid layer containing the sensitizer.

2. The process of sensitizing finished bleaching-out layers which comprises bringing a bleaching-out layer into contact with a colloid layer 4. In sensitizing bleaching-out layers the step which comprises pouring a. solution of colloid and sensitizer onto a non-sensitized bleaching-out layer.

5. In sensitizing bleaching-out layers the step 'which comprises pouring a solution of ellylthiourea' and gelatin in water on to a non-sensitized bleaching-out layer comprising gelatin as binding agent.

BRUNO ALFRED mbmcn. 

